Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 041206
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
806 AM EDT SAT JUL 4 2015

.SYNOPSIS...
A BROAD UPPER LEVEL TROUGH WILL REMAIN OVER THE SOUTHEAST THROUGH
MONDAY...PROVIDING LIFT AND MAINTAINING ELEVATED RAIN AND
THUNDERSTORM CHANCES EACH DAY. SLIGHTLY DRIER CONDITIONS RETURN
TUESDAY AND WEDNESDAY...BEFORE ANOTHER FRONT PUSHES ACROSS THE
SOUTHERN APPALACHIANS BY THE END OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 700 AM EDT SATURDAY...TWEAKED POPS/SKY TO ACCOUNT FOR
CURRENT LIGHT PRECIP COVERAGE. ALSO ADJUSTED TEMPERATURES AND
DEWPOINTS TO BETTER REFLECT MOST RECENT OBS...NO OTHER CHANGES
WERE MADE AS CURRENT FCST REMAINS ON TRACK.

PREVIOUS DISCUSSION...

AS OF 325 AM EDT SATURDAY...RATHER ROBUST BAND OF CONVECTION
ASSOCIATED WITH DEEP LAYER INSTABILITY CONTINUES TO SLIDE ALONG THE
I20 CORRIDOR FROM EASTCENTRAL GA INTO THE SC MIDLANDS.  LATEST SPC
MESOANALYSIS CONTINUES TO INDICATE A MODESTLY UNSTABLE ENVIRONMENT
OVER THESE AREAS...WHILE SHOWING A RATHER SHARP DECREASING GRADIENT
NORTHWARD INTO THE SC UPSTATE.  FURTHER WEST ANOTHER BAND OF BROKEN
CONVECTION STRETCHED IN A NORTH/SOUTH ORIENTATION FROM SOUTHEAST TN
SOUTHWARD TO AROUND COLUMBUS GA.  IT IS THIS CONVECTIVE ELEMENT THAT
LATEST CAMS PROG WILL SURVIVE/ADVANCE INTO NORTHEAST GA AND THE
WESTERN CAROLINAS BY AROUND DAYBREAK.

FOR THE REMAINDER OF THE HOLIDAY...THE PATTERN IS SOMEWHAT SIMILAR
TO THAT OF YESTERDAY AS IT IS HIGHLIGHTED BY A BROAD POS TILTED
UPPER TROF...AND A QUASI STATIONARY CONVERGENCE AXIS ACROSS THE TN
VALLEY.  THIS SURFACE FEATURE COMBINED WITH LOBES OF VORTICITY
AROUND THE UPPER TROF...ALL ENHANCED BY REAR ENTRANCE REGION OF
UPPER JET...WILL SUPPORT SCATTERED/NUMEROUS SHOWERS AND
THUNDERSTORMS ONCE AGAIN TODAY.  ALSO SIMILAR TO THAT OF YESTERDAY
WILL LIKELY BE THE EVOLUTION OF THE INSTABILITY PARAMETERS ACROSS
THE REGION WHICH WILL BE GREATLY IMPACTED BY AM
CONVECTION...ESPECIALLY OVER THE SOUTHERN TIER OF THE FCST AREA.
20-30KTS 0-6KM BULK SHEAR WILL ONCE AGAIN BE PRESENT IN THE
PROFILES...HOWEVER ITS SEEMS THE ABOVE MENTIONED FAULTS IN
INSTABILITY WILL PREVAIL LEADING TO ONLY A FEW STRONG STORMS AT BEST
THIS AFTERNOON.  PWATS REMAIN AROUND 2 INCHES WHICH WILL LEAD TO
CONTINUED FLASH FLOODING THREATS WHERE ANY CELL TRAINING OCCURS.
PLANS ARE TO EXPAND/EXTEND CURRENT FLASH FLOOD WATCH TO ACCOUNT FOR
MOST RECENT PRECIP/FFG VALUES IN THE NEAR TERM...AND BEYOND INTO THE
SHORT TERM.  LATEST QPF REMAINS VERY SIMILAR TO THAT OF LAST FCST
CYCLE WHICH FOCUSES MAINLY ON THE SW MTNS OF WESTERN NC...AND
NORTHEAST GA WHERE UPWARDS OF 1-2 INCHES IS FEATURED.
HOWEVER...THOSE NUMBERS COULD BE UNDERSTATED IF/WHEN TRAINING OF
CELLS OCCURS.

ALL SAID...THE INDEPENDENCE DAY FCST FEATURES SCATTERED TO NUMEROUS
POPS FOR SHRA/TSRA THIS MORNING ACROSS THE UPSTATE AND UPPER SAVANNAH
RIVER VALLEY...BEFORE TAPERING TO CHANCE LEVELS THIS AFTERNOON.  AT
THAT TIME THE HIGHEST POPS WILL RESIDE OVER THE HIGH TERRAIN...AND
ALSO ALONG AND NORTH OF I40 IN THE WESTERN NC PIEDMONT WHERE LIKELY
LEVELS ARE MENTIONED.  SKIES WILL BE MOSTLY CLOUDY WITH BELOW NORMAL
TEMPERATURES.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 315 AM INDEPENDENCE DAY...ON SUNDAY THE KEY FEATURES WILL
CONTINUE TO BE A BROAD UPPER SHORTWAVE CENTERED OVER THE UPPER TENN
VALLEY...AND A WEAK LOW LEVEL BOUNDARY OVER THE CAROLINAS.
DIFFERENCES IN THE PATTERN ARE MINOR COMPARED TO SATURDAY. DEEP
MOISTURE WILL ACTUALLY BE SLIGHTLY BETTER...CHARACTERIZED BY PWAT
VALUES ABOVE THE 90TH PERCENTILE PER SPC RAOB CLIMO. THIS IS IN PART
DUE TO A BETTER GULF CONNECTION...ON ACCOUNT OF LOW LEVEL WINDS
BACKING TO SOUTHWEST IMMEDIATELY AHEAD OF THE UPPER TROUGH. THIS WILL
ENHANCE UPSLOPE FORCING INTO THE SW PORTION OF THE CWFA AS WELL.
FURTHERMORE WIND PROFILES WILL FEATURE WEAK AND NEARLY UNIDIRECTIONAL
SHEAR. THE CONCERN ACCORDINGLY WILL CONTINUE TO BE FOR THUNDERSTORMS
PRODUCING HEAVY RAIN AND POTENTIALLY TRAINING. WITH THE INGREDIENTS
CONTINUING TO BE IN PLACE FOR A FLOOD THREAT...WE HAVE EXTENDED THE
FLASH FLOOD WATCH ANOTHER 24 HOURS...NOW ENDING AT 00Z MONDAY. ALSO
THE AREA HAS EXPANDED TO ALL OF JACKSON CO...OCONEE CO...AND THE
REMAINDER OF OUR NE GA COUNTIES. THESE AREAS HAVE THE LOWEST FFG
VALUES AS WELL AS GREATER POTENTIAL FOR UPSLOPE ENHANCEMENT. MAX
TEMPS WILL CONTINUE TO BE BELOW CLIMO...SIMILAR TO SATURDAY.

ON MONDAY THE TROUGH WILL LIFT NEWD ACRS THE AREA...AND BEGIN TO
MERGE WITH A LARGER SCALE SHORTWAVE ENTERING THE UPPER MISSISSIPPI
VALLEY. THE INFLUENCE OF THE TROUGH ON LIFT WILL BE LESSER...AND
PROFILES ARE LESS CONDUCIVE TO HEAVY RAIN PRODUCTION. HOWEVER
ISOLATED FLOODING CANNOT BE RULED OUT. POPS IN GENERAL WILL BE LOWER
PARTICULARLY OVER THE SRN HALF OF THE CWFA. DESPITE LESS CLOUD COVER
AND PRECIP...TEMPS MAY BE SLIGHTLY COOLER DUE TO LOWER THICKNESSES
BENEATH THE TROUGH. SO VALUES STILL TOP OUT A CATEGORY OR TWO BELOW
CLIMO.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 130 AM INDEPENDENCE DAY...HEIGHTS START TO RISE TUESDAY AS
UPPER LOW IS ABSORBED INTO THE NRN STREAM AND SUBTROPICAL RIDGE
REGAINS STRENGTH OVER THE SOUTHEAST. MIDLEVEL LAPSE RATES ACCORDINGLY
WEAKEN FROM DAY TO DAY...SO DIURNAL CONVECTIVE POTENTIAL WILL RETURN
TO NEAR CLIMO...WITH MAINLY JUST SHOWERS MENTIONED. AS A SHORTWAVE
MOVES ACRS ONTARIO/QUEBEC A COLD FRONT WILL SAG INTO THE OHIO VALLEY
WED...WITH HIGH PRESSURE BUILDING EWD BEHIND IT. THE PRESENCE OF THIS
FEATURE LIMITS OUR CONFIDENCE GOING FORWARD. IT IS A SEASONABLY WEAK
BOUNDARY...HOWEVER GLOBAL MODELS HINT THAT A WAVE WILL DEVELOP ALONG
IT SOMEWHERE TO OUR WEST...THOUGH THEY DIFFER IN THE DETAILS. GFS/GEM
DEPICT THE WAVE TRACKING ALONG OR N OF THE OHIO RIVER...MAINLY
KEEPING THE FRONT ON OUR NWRN FRINGE. THE EC ON THE OTHER HAND
DEVELOPS A STRONGER WAVE OVER THE SRN PLAINS...LEADING IT TO DELAY
ITS PUSH ACRS THE MTNS UNTIL FRI. HOWEVER THIS ALSO IMPLIES A MORE
BULLISH FRONT. WILL BRING POPS BACK UP SLIGHTLY THU AND THU NIGHT.
TEMPS WILL WARM BACK TO NEAR NORMAL BY WED.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...VFR WITH THE EXCEPTION OF MORNING/AFTERNOON CONVECTION
LEADING TO RESTRICTIONS.  STALLED BOUNDARY IN THE VICINITY
OF THE CAROLINAS CONTINUES TO YIELD AN UNSETTLED PATTERN WITH
SCATTERED SHRA/TSRA FAVORED.  THUS...THE TAF INITIALIZES DRY UNDER
BKN MID CLOUDS AND GUSTY SW WINDS WITH A 4HR TEMPO FOR SHRA.  WINDS
WILL REMAIN ELEVATED OUT OF THE SW THROUGH THE DAY WITH GUSTS AS
HIGH AS 20-25KTS POSSIBLE DURING MIXING HOURS.  PROB30 FOR TSRA WILL
PREVAIL FOR THE AFTERNOON.  CONDITIONS WILL IMPROVE INTO THE EARLY
EVENING WHERE BKN MID AND OVC HIGH LEVEL CLOUDS PREVAIL.

ELSEWHERE...SIMILAR TO THAT OF KCLT ABOVE WHERE MULTIPLE ROUNDS OF
SHRA/TSRA ARE FCST AT ALL SITES ON SATURDAY.  ALL SITES FEATURE WX
MENTION IN THE FORM OF SHRA/VCSH ALONG WITH MVFR CIGS THIS MORNING
ASSOCIATED WITH INITIAL ROUND OF CONVECTION...WITH FURTHER SHRA/VCTS
MENTION THIS AFTERNOON TO ACCOUNT FOR ADDITIONAL ACTIVITY.
INCREASING SW WINDS AT THE SC SITES WILL LEAD TO YET ANOTHER
WINDY/GUSTY DAY WITH GUSTS AS HIGH AS 25-30KTS POSSIBLE.  EXPECTING
CONDITIONS TO IMPROVE INTO THE EARLY EVENING AS STATED ABOVE.

OUTLOOK...PRECIPITATION COVERAGE WILL REMAIN HIGH THROUGH
SUNDAY...THEN THE PATTERN WILL TRANSITION TO A MORE DIURNAL
PATTERN...BUT WITH CONTINUED MOISTURE IN THE AREA. RESTRICTIONS WILL
BE CONFINED MAINLY TO THUNDERSTORMS AND THEN EARLY MORNING STRATUS
WHERE HEAVY RAIN FELL THE PREVIOUS DAY.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  99%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  81%     HIGH  96%     HIGH 100%     MED   72%
KHKY       HIGH  97%     HIGH  99%     HIGH 100%     HIGH 100%
KGMU       HIGH  99%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLASH FLOOD WATCH THROUGH SUNDAY EVENING FOR GAZ010-017-018-
     026-028-029.
NC...FLASH FLOOD WATCH THROUGH SUNDAY EVENING FOR NCZ048-051-052-
     058-059-062-063.
SC...FLASH FLOOD WATCH THROUGH SUNDAY EVENING FOR SCZ001-004.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...CDG
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...CDG


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